Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
KVM: x86/xen: Fix runstate updates to be atomic when preempting vCPU
commit fcb732d upstream. There are circumstances whem kvm_xen_update_runstate_guest() should not sleep because it ends up being called from __schedule() when the vCPU is preempted: [ 222.830825] kvm_xen_update_runstate_guest+0x24/0x100 [ 222.830878] kvm_arch_vcpu_put+0x14c/0x200 [ 222.830920] kvm_sched_out+0x30/0x40 [ 222.830960] __schedule+0x55c/0x9f0 To handle this, make it use the same trick as __kvm_xen_has_interrupt(), of using the hva from the gfn_to_hva_cache directly. Then it can use pagefault_disable() around the accesses and just bail out if the page is absent (which is unlikely). I almost switched to using a gfn_to_pfn_cache here and bailing out if kvm_map_gfn() fails, like kvm_steal_time_set_preempted() does — but on closer inspection it looks like kvm_map_gfn() will *always* fail in atomic context for a page in IOMEM, which means it will silently fail to make the update every single time for such guests, AFAICT. So I didn't do it that way after all. And will probably fix that one too. Cc: stable@vger.kernel.org Fixes: 30b5c85 ("KVM: x86/xen: Add support for vCPU runstate information") Signed-off-by: David Woodhouse <dwmw@amazon.co.uk> Message-Id: <b17a93e5ff4561e57b1238e3e7ccd0b613eb827e.camel@infradead.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
- Loading branch information
Showing
1 changed file
with
67 additions
and
30 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters